Tk. 5000 becomes Tk. 6200 in 3 years at a certain rate of simple interest. If the rate becomes double, what will be the total amount in 4 years on the same principal?

Question: Tk. 5000 becomes Tk. 6200 in 3 years at a certain rate of simple interest. If the rate becomes double, what will be the total amount in 4 years on the same principal? Solution:Principal = Tk. 5000Amount after 3 years = Tk. 6200∴ Interest in 3 years = 6200 - 5000 = Tk. 1200∴Interest per year = 1200/3 = Tk. 400Since the interest rate doubles, the yearly interest also doubles,∴ Interest per year = 400 × 2 = Tk. 800⇒ Interest for 4 years = 800 × 4 = Tk. 3200⇒ New total amount = 5000 + 3200 = Tk. 8200